Nuts and bolts of the endocrine system Flashcards
The hypophysis is a compound gland suspended from the hypothalamus by which structure?
infundibulum
Where is the hypophysis located?
sella turcica, sphenoid bone
What is the function of the hypophysis?
‘master’ endocrine gland. produces several hormones that influence activity of other endocrine glands (e.g. liver)
What are the two divisions of the hypophysis?
adenohypophysis: anterior lobe, glandular part, outpouching of ectoderm of oral cavity – Rathke’s pouch.
neurohypophysis: posterior lobe, neural part, downgrowth from diencephalon of brain.
What is the blood supply to the hypophysis?
branches of internal carotid:
superior hypophyseal artery - median eminence, upper part of stalk.
inferior hypophyseal - neurohypophysis, lower part of stalk.
arteries supplying median eminence and stalk end as capillary plexuses.
Outline the venous drainage of the hypophysis and what does this setup provide?
capillary plexuses in median eminence and stalk ending are drained by portal veins.
these veins pass to anterior lobe of pituitary and form a secondary capillary plexus.
this provides a route for neurosecretory substances released from hypothalamus to also reach the anterior lobe.
Describe the thyroid gland and its location
bilobed gland in neck.
2 lateral lobes connected by an isthmus that courses anterior to trachea.
from just below oblique line of thyroid cartilage to 5/6 tracheal ring, immediately anterior to trachea.
Where is the thyroid gland derived from and which structures control the thyroid gland?
from endoderm, develops as a growth from floor of pharynx.
hypothalamus (TRH) and hypophysis (TSH).
What is the blood supply and drainage of the thyroid gland?
Arteries: superior thyroid from external carotid. inferior thyroid from subclavian. Veins: from an extensive plexus into internal jugular vein brachiocephalic vein
Describe the size and locations of the parathyroid glands
4 parathyroid glands: 2 superior and 2 inferior.
embedded in capsule of thyroid, posterior aspect.
very small, about the size of a grain of rice.
What is the role of parathyroid glands?
secrete parathyroid hormone – regulates calcium and phosphate levels within homeostasis
Which vessels and nerves supplies and drains the parathyroid glands?
primarily inferior thyroid artery (also superior).
superior, middle and inferior thyroid veins.
middle and inferior cervical ganglions.
What is the shape and location of the adrenal glands?
pyramidal (R) or semilunar (L).
superior pole of kidneys (T12), retroperitoneal.
What is the blood supply to the adrenal glands?
Superior (from inferior phrenic), middle (from aorta) and inferior suprarenal arteries (from renal).
Cortical arteries give rise to subcapsular plexus and in turn to cortical sinusoids that distributes blood to cortical cells.
Medullary arteries pass through cortex to supply medulla (receives blood from two sources).
Adrenal veins drain into IVC (R) or renal vein (L).
How is the activity of the adrenal glands controlled?
Hypothalamus, e.g. ACTH release from hypophysis. Sympathetic division of ANS: coeliac plexus, splanchnic nerve.
ACTH stimulates secretion of corticosteroids.
Medulla is under direct control from ANS (sympathetic) - fast response.
Release is initiated by impulses from preganglionic sympathetic fibres that end in chromaffin cells of medulla. Chromaffin cells then release catecholamines into adjacent circulation.
